Imaizumi, a typical high‑school student, finds his home turned into a casual spot for three classmates. The story opens with the girls playing a game in his bedroom, while one of them leans in to hug him from behind. The other two girls grow thirsty and head to a nearby shop for snacks, leaving the boy and the blonde girl at home. When the blondie returns, she takes initiative. On re‑entering, they witness the boy and girl together in an intimate moment. The girls cannot help but admire how impressive his… is, prompting them to shift into a new type of game. Their playful curiosity turns into an unexpected adventure as they explore the boundaries of friendship.
